Quinone Based Conducting Redox Polymers for Electric Energy Storage

Abstract

Conducting redox polymers (CRP), consisting of conducing polymer (CP) and a redox active pendant group (PG) covalently linked to the CP backbone, have been suggested as electrode materials for secondary batteries. This type of material could provide an alternative to inorganic electrode materials and is favorable because of its renewability and sustainability (figure 1). Redox active organic compounds have previously been used as electrode materials for secondary batteries. However, due to the dissolution of many interesting compounds in common battery electrolytes, they suffer from poor recyclability and, in addition, the limited conductivity in these materials requires addition of substantial amounts of conductivity additives in the electrode formulation. By introducing a CP as backbone, not only the dissolution issue is solved, but also the conductivity will be greatly improved. In our studies, we choose polypyrrole as CP, and p-benzoquinone as PG. Polypyrrole has been extensively studied and the electrochemistry and charge transport in this system is well understood. The corresponding knowledge of charge transport in CRPs is however to a large extent lacking. With the aid of temperature dependent in-situ conductivity measurements during the polymer doping process, mechanistic information on the charge transfer in quinone-based CRPs was investigated. Additionally, by varying the link between the two subunits the effect of linker on the performance of the materials was studied. With assistance of various in situ techniques, such as in situ conductivity measurement, in situ ATR-FTIR, EQCM, the interaction between the CP and PG was probed. It was found that the choice of linker has a substantial impact on the charge transport properties of the material. The insight gained from investigating the interaction between these two subunits will benefit further molecular variation of quinone-based electrode materials for secondary batteries. Figure 1